Electrical properties of electronic parts such as integrated circuits (ICs), large-scale integrated circuits (LSIs) and light-emitting diodes (LEDs) (in other words, electronic parts using semiconductor elements) are tested by bringing a contact probe into contact with an electrode of a semiconductor element. Such a contact probe used in the test device not only has low conductivity, that is, a low contact resistance value but also is required to have conductivity without deteriorating even with repeated contact with an electrode that is an adherend.
A contact resistance value of a contact probe is generally set to 100 mΩ or less, but sometimes deteriorates to several hundred mΩ to several Ω by repeated tests with the adherend. As a countermeasure thereto, cleaning or replacement of a contact probe has been carried out. However, such a countermeasure significantly lowers the reliability of a test process and an operating rate of a test device, and therefore, it has been desired to realize a contact probe having a property that contact resistance value does not deteriorate even when in use for a long period of time. Particularly, when solder, tin, or the like is formed on an electrode that is an adherend, since the surface thereof is easily oxidized and soft, the surface is scraped off by contact of the contact probe, thereby generating a property of easily adhering to the tip part of the contact probe and causing stable contact to be difficult.
For example, Patent Document 1 discloses a hard carbon film formed of carbon or carbon and hydrogen and the electrical resistivity of which is altered in the thickness direction in order to improve the adhesiveness between the hard carbon film and the base material, as the hard carbon film which can be applied to coating with mold releasability or the like for preventing adhesion of a soft metal such as solder or Al. However, Patent Document 1 does not mention application to a contact probe or indicate any consideration on conductivity.
As a technology for stabilizing contact resistance value of the contact probe, for example, Patent Documents 2 to 5 can be exemplified. Patent Documents 2 to 5 disclose that a carbon film such as DLC (Diamond Like Carbon) formed on the surface of a contact terminal with an electrode of a semiconductor element is made to contain a metal element such as tungsten, thereby realizing a surface film having both of a low adhesion property to other material(s) and high conductivity resulting from the contained metal.